This invention relates to automatic and semi-automatic power transmissions providing a plurality of gear reduction ratios, such as vehicular automatic mechanical transmissions (i.e. "AMTs"), and, to control systems and methods therefor. In particular, the present invention relates to control systems and methods for vehicular automatic/semi-automatic mechanical transmission systems wherein gear selection and/or shift decisions are made and/or executed based upon measured and/or calculated parameters such as engagement condition of the transmission, vehicle or transmission output shaft speed, transmission input shaft speed, engine speed, throttle position, rate of change of throttle position, rate of change of vehicle and/or engine speed and the like. More particularly, the present invention relates to a method/system for controlling an AMT system utilizing sensors for providing input signals indicative of the presence of a transmission gear neutral condition, engine, transmission input shaft and transmission output shaft rotational speeds, etc. including sensing of a faulty signal from the gear neutral sensors and modifying the system operation logic in response to detection of such fault.